Question: What do the following two equations represent? $-3x+3y = -1$ $-9x-9y = -5$
Solution: Putting the first equation in $y = mx + b$ form gives: $-3x+3y = -1$ $3y = 3x-1$ $y = 1x - \dfrac{1}{3}$ Putting the second equation in $y = mx + b$ form gives: $-9x-9y = -5$ $-9y = 9x-5$ $y = -1x + \dfrac{5}{9}$ The slopes are negative inverses of each other, so the lines are perpendicular.